Senegal River Delta Research Articles

A comprehensive assessment for agriculture water requirement main crops of the Senegal River delta

A comprehensive assessment for agriculture water requirement main crops of the Senegal River delta

Identification of Bulinus forskalii as a potential intermediate host of Schistosoma hæmatobium in Senegal.

Understanding the transmission of Schistosoma hæmatobium in the Senegal River Delta requires knowledge of the snails serving as intermediate hosts. Accurate identification of both the snails and the infecting Schistosoma species is therefore essential. Cercarial emission tests and multi-locus (COX1 and ITS) genetic analysis were performed on Bulinus forskalii snails to confirm their susceptibility to S. hæmatobium infection. A total of 55 Bulinus forskalii, adequately identified by MALDI-TOF mass spectrometry, were assessed. Cercarial shedding and RT-PCR assays detected 13 (23.6%) and 17 (31.0%), respectively, Bulinus forskalii snails parasitized by S. hæmatobium complex fluke. Nucleotide sequence analysis identified S. hæmatobium in 6 (11.0%) using COX1 and 3 (5.5%) using ITS2, and S. bovis in 3 (5.5%) using COX1 and 3 (5.5%) using ITS2. This result is the first report of infection of Bulinus forskalii by S. hæmatobium complex parasites in Senegal using innovative and more accurate identification methods to discriminate this snail and characterize its infection by S. hæmatobium.

Size class, density, and distribution of Uca tangeri (Eydoux, 1835; Decapoda: Ocypodidae) in the mangrove ecosystems of Senegal

This study focusing on the decapod brachyuran Uca tangeri is the first of its kind in Senegal. It was carried out in the mangroves of the Senegal River delta, the Saloum islands, and the Casamance estuary. The modal cephalothoracic length (L; mm) is between 24 and 25 mm in Saint-Louis, 18 and 19 mm in the Saloum, and 16 and 17 mm in Casamance. The modal cephalothoracic weight (Wei; mm) oscillates between 31 and 32 mm in Saint-Louis, 24 and 25 mm in the Saloum, and 25 and 26 mm in Casamance. Whether it is the relation Lc/We or that of the height/weight, the allome-tric growth of crabs is negative (b 0.8) among the biometric parameters. The average crab density in the mangrove is between 1.3 and 1.6 crabs per square meter. The strong presence and abundance of Uca tangeri suggest this species does not have a preferential spatial distribution.

Beyond controversy, putting a livestock footprint on the map of the Senegal River delta

The Senegalese delta, like many other agricultural territories in the Global South, is experiencing changes in agricultural trajectory. These changes are related to the promotion of competitive and performance-based forms of agriculture. In a context of tense relations between farmers and herders, the quest for equitable access to land, which is a guarantee of peace, stability, and balanced economic and social development, is being called into question by the arrival of capital investors and new actors that are highly supported by the State. This situation raises questions about two important issues: (i) the challenge of the sustainable management of natural resources, especially land; and (ii) the socio-political stakes related to the fact that land is a sensitive resource, both politically and socially. The situation is exacerbated by the fact that dominant discourses are being built around representation of unused and available lands. The aim of this article is to address this controversy by questioning land-use planning processes and tools and underlining the reality depicted. We demonstrate that discourses around land availability are built upon sectoral visions that tend to overshadow the realities of land use. Indeed, livestock farming and particularly its mobile form (i.e., pastoralism) is rendered invisible by not being considered in the majority of land-use and agricultural policies. Through a participatory survey of campsites, we show that gathering basic information on livestock farming should not to be reduced to technical issues. Beyond that, we acknowledge that these land-use issues are rooted in sector-based and neoliberal visions of development. We conclude by discussing the importance of effective decentralization in financial and technical means and the development of systemic proficiency that goes beyond normative sectoral views to acknowledge and act on territorial development.

La place des jeunes africains sur les périmètres irrigués dans un contexte de libéralisation et de partenariat public privé : le cas des jeunes agriculteurs du delta du fleuve Sénégal

This article analyzes different approaches to establishing rural youth in irrigation areas in the Senegal
 River delta in the context of new hydro-agricultural developments and massive land acquisitions by agrobusiness.
 Government-led irrigation projects introduced in the 1960s distributed free 0.2-hectare plots of
 land to young workers from the surrounding region. However, in the 1980s, Senegal took a liberal turn
 that led to a shift from public-sector to private-sector initiatives. As a result, young workers, who often
 lack the means necessary to acquire land, have found it much more challenging to pursue farming in
 irrigation areas. Since 2006, few young farmers have acquired any of the 5,000 hectares of new irrigated
 farmland developed through programs based on the public-private partnership model. At the same time,
 agro-industry growth has provided young people with many temporary and precarious employment
 opportunities.
 
 Based on surveys of farmers and agricultural workers in the Senegal River delta, we show how young
 people find it increasingly difficult to acquire land or secure adequate employment in the agricultural
 sector. In addition, we demonstrate that access to irrigated land, as opposed to salaried agricultural work,
 represents the most effective strategy for poverty reduction.

Determination of the Hydrodynamic Parameters of Two Types of Soil in the Senegal River Delta. Simulation of Hydro-saline Transfers: Application to the Wind Deflation Phenomenon

In the Senegal River delta, the presence of a shallow salt water table associated with a strong evaporative demand sometimes leads to an upwelling of salts that crystallize on the surface. This phenomenon can be observed in the vicinity of the Diawling Basin, where a powdery structure sensitive to wind deflation and a massive structure with a fractionation into platelets that cannot be transported by the wind are noted.
 To understand the hydrodynamic characteristics of these soils, we used numerical simulation of water and solute transfers. The hydrodynamic parameters were determined in the laboratory using Wind's method on undisturbed samples. The experimental retention h() and hydraulic conductivity K(h) curves were fitted using the Van Genuchten model. The simulations show that the soil with a powdery structure has hydrodynamic characteristics that favour the ascent of salts from the water table to the surface. For the soil with a massive structure, the hydrodynamic conditions impose a deposition of salts in the subsurface.

Impacts of Irrigation Water on the Hydrodynamics and Saline Behavior of the Shallow Alluvial Aquifer in the Senegal River Delta

The Senegal River Delta located in north-western Senegal is a strategic region for the development of irrigated rice cultivation for achieving rice self-sufficiency. The presence of a shallow salty water table is often considered as a brake to the development of irrigation, by causing salinization of the soil, although the mechanisms of operation are not well known. An experimental study was carried out in a rice paddy located in the village of Ndiaye, 35 km north from Saint Louis, to characterize the water and solute flux processes below the irrigated plots. The objective was to better understand the irrigation-driven dynamics of soil salinization processes. An experimental monitoring network was installed for monitoring the transit of water at the plot level, in the unsaturated zone and in the aquifer. The results show that the supply of water by irrigation contributes to significantly recharging the water table, as shown by the rise in piezometric level, with a concomitant dilution of the water salinity in the soil zone and in the shallow groundwater. However, when irrigation is stopped, the groundwater level and salinity return within a month to their initial level and salinity status because of the evaporative recovery, which strongly governs these processes. Thus, water flow and solute transfers operate in the delta following a recharge–discharge and dilution–concentration cycle controlled by the water balance, and we do not expect to observe in the short- to middle-term any significant reduction in soil salinization processes by drainage.

Management of the Water Slide Brought and Saline Flow in Irrigated Onion (<i>Allium cepa</i> L.) Cultivation in the Senegal River Delta

The find for the optimal slide of water to bring to the plot during the irrigated onion crop was important in order to limit the recharge of the water table close to the soil surface. The quantities of water supplied during onion irrigation were estimated from measurements made with a metal crest to the plot positioned at the tertiary canal. The flow rates at the tertiary canal directly irrigating the plot were recorded during irrigation. From this flow rate, the quantity of water supplied to each plot was determined. From then, the performance of the irrigated system in onion cultivation should pass on the management of this water slide at the level of the hydroagricultural facilities. The integrated soil water mass, salinity and water table dynamics monitoring system was used to assess the water requirements of onion following the irrigation. The daily water requirement of onion in the holland soil of the delta was estimated to average 0.45 g/m3. These requirements were varied according to the development stage of the crop. The water level between the ridges was between 6 and 9 mm during irrigation. This was not permanent, it infiltrated between 12 and 18 hours. This type to the stingray irrigation did not favour the arrival of the water table on the surface. The only fluctuations in the water table were observed during the bulb maturation phase. During this phase, the soil water masses were important. The electrical conductivity recorded varied during the campaign. At the beginning of irrigation, it was 3.62 mS/cm on a 30 cm profile, it decreased towards the end of the irrigations to reach 2.06 mS/cm. The quantities of salt recorded on a 30 cm profile varied from one month to the next; they were 0.468 t/ha at the beginning of irrigation (January) and 0.275 t/ha at the end of the campaign (April). From these results we can say that land degradation in the Senegal river delta would be linked to the arrival of salty groundwater on the surface.

It’s risky to wander in September: Modelling the epidemic potential of Rift Valley fever in a Sahelian setting

Estimating the epidemic potential of vector-borne diseases, along with the relative contribution of underlying mechanisms, is crucial for animal and human health worldwide. In West African Sahel, several outbreaks of Rift Valley fever (RVF) have occurred over the last decades, but uncertainty remains about the conditions necessary to trigger these outbreaks. We use the basic reproduction number (R0) as a measure of RVF epidemic potential in northern Senegal, and map its value in two distinct ecosystems, namely the Ferlo and the Senegal River delta and valley. We consider three consecutive rainy seasons (July-November 2014, 2015 and 2016) and account for several vector and animal species. We parametrize our model with estimates of Aedes vexans arabiensis, Culex poicilipes, Culex tritaeniorhynchus, cattle, sheep and goat abundances. The impact of RVF virus introduction is assessed every week over northern Senegal. We highlight September as the period of highest epidemic potential in northern Senegal, resulting from distinct dynamics in the two study areas. Spatially, in the seasonal environment of the Ferlo, we observe that high-risk locations vary between years. We show that decreased vector densities do not greatly reduce R0 and that cattle immunity has a greater impact on reducing transmission than small ruminant immunity. The host preferences of vectors and the temperature-dependent time interval between their blood meals are crucial parameters needing further biological investigations.

Extractivism, exclusion and conflicts in Senegal’s agro-industrial transformation

ABSTRACT In the last two decades, the promotion of agro-industry has become a dominant developmental imperative on the African continent, leading to efforts to involve private-sector actors. This article examines the political economy and ecology of agro-industry in the Senegal River delta, focusing on local-level reactions to Senegalese initiatives aimed at attracting foreign investors in agriculture. The argument is that Senegal is witnessing the emergence of an agro-extractivist pattern that replaces earlier development objectives – such as peasants’ integration into the national economy – with the new imperative of the integration of territories into global capitalism. The article presents empirical evidence on three main consequences of the increased presence of agro-industry: a process of change in land property and access; the end of public support to peasant farmers; and an intensified marginalisation of pastoralism. Colonial heritage and the role of local resistances in shaping and mediating this developmental strategy are also discussed.

Does Diversification Lead to Livelihood Security in Fishing-Farming Communities? Insight from the Senegal River Delta

Livelihood diversification is often regarded as a mechanism to reduce poverty, making rural communities more resilient to resource fluctuations. However, despite engaging in diversification, many rural households continue to grapple with poverty and vulnerability. We explore the extent to which livelihood diversification reduces vulnerability of resource-dependent livelihoods and the factors shaping these outcomes. We specifically examine fishing households also engaged in farming as a supplementary income-generating activity in three communities in the Senegal River Delta. We apply a framework built on the concepts associated with livelihood security (i.e., income, asset, food, and nutritional security). We address the question of how and why engaging in farming as a livelihood diversification strategy enhances the livelihood security of some fishing households but not others. Overall, we found that commercial horticulture (irrigated) rather than rain-fed agriculture was more effective at reducing household seasonal vulnerability to food and income insecurity, in addition to improving nutritional security at the community level. Furthermore, households that collected high farm revenues were able to build their productive assets by purchasing fishing gears and livestock. Underlying factors shaping these outcomes included risk, crop diversity, household debt accrued, livestock holdings, and technical knowledge.

Rice genotype and fertilizer management for improving rice productivity under saline soil conditions

Soil salinity is a threat to crop production in the Senegal River Delta where salt intrusion increases soil electrical conductivity and most of farmers had abandoned their rice farms. The objective of this study was to evaluate an integrated management to improve rice productivity under saline soil condition in the Senegal River Delta. Field experiments were conducted during four rice-growing seasons from July 2014 to July 2016 at Africa Rice Center research station at Ndiaye, Senegal. The performance of five rice genotypes (IR63275-B-1-1-3-3-2, WAS73-B-B-231-4, NERICA-L9, FL478, and IR29) was evaluated under three salinity levels (0.5–0.8 dS m−1, 2.0 dS m−1, 3.5 dS m−1) and two fertilizer management options (basal dressing at 100 kg ha−1 of N–P–K (15–15–15) only and basal dressing at 200 kg ha−1 of N–P–K (15–15–15) + 50 kg N ha−1 urea at panicle initiation and at booting. Rice seedlings were raised at nursery for 21 days and transplanted at the density of 20 cm × 20 cm around March 15 and August 15 and harvested around July 15 and early December. The plots were drained canal when soil EC increased 0.1 dS m−1 above the designed EC levels. The results showed that rice yield decreased with the increasing soil salinity and were season dependent. Rice grain yield varied from 0.9 to 8 tons ha−1. Rice grain yield was 20% higher during the hot and dry seasons than the wet season. The application of the recommended fertilizer improved rice yield by 52% compared to the basal fertilizer application only. Nitrogen application at panicle initiation and at booting stages in addition to the basal fertilizer application doubled rice grain yield and should be adopted under salinity condition across the Senegal River Delta. The analysis of the combination of yield index, yield stability index, stress susceptibility index and the stress tolerant index indicated that the newly developed rice genotypes IR63275-B-1-1-3-3-2 and WAS73-B-B-231-4 showed high salt tolerance with better yield stability and low stress susceptibility and constitute good candidate to be adopted under the best fertilizer management option in the Senegal River Delta climate, soil salinity and similar environmental conditions.

Impact of Agribusiness Contract on Smallholder Farmers’ Incomes in Senegal Delta River and Mauritius

Agribusiness is one of the policy options in most countries to ensure food security, reduce poverty and support family farming towards modernization. Under these conditions, farmers and agribusiness companies are entering into agricultural contracts in some developing countries, like Senegal and Mauritius. This research aims to evaluate the impact of agribusiness contracts on farmers' incomes in the Senegal River Delta and Mauritius. The sample surveyed is 270 farmers in Mauritius (93 treated) and 320 in the Senegal Delta (147 treated), coupled with interviews and bibliographic research. To analyze the data, we used the propensity score matching method based on the counterfactual approach. The impact of agricultural contracts on farmers' incomes in Mauritius is € 1,648 per agricultural season with a threshold of 10% of significance. In the Senegal Delta, this impact is € 505, but it is not significant. This research therefore suggests that agribusiness production contracts are more favorable to improve the agricultural income of family farms. Keywords: agricultural contract, family farm, impact, income. DOI : 10.7176/JESD/10-12-10 Publication date :June 30 th 2019

Influence of physicochemical parameters on the spatial distribution of snail species that are intermediate hosts of human schistosomes in the Senegal River Delta.

The objective of this work was to identify possible correlations between physicochemical parameters (water temperature, water flow velocity, electrical conductivity, dissolved oxygen, salinity, pH, nitrates, and phosphates) and the spatial distribution in the Senegal River delta of snail species that are intermediate hosts of human schistosomes. Eight water points (ME1 to ME4, NE1 and NE2, TA1 and TA2) were selected in the villages of Menguègne Boye, Ndellé Boye, and Thilla for biweekly monitoring of these snails and the physicochemical parameters of the water. The results show that the spatial distribution of the snail populations is related to pH, dissolved oxygen (mg/l), conductivity, temperature (̊C), and water flow velocity (m/s).

Quantitative Estimation of Recharge Potentialities of Shallow Aquifers in Senegal River Delta Hydrosystem

The objective of this paper is to assess quantitatively the potential recharge of shallow aquifers in the Senegal River delta in context of semi-arid climate, of massive irrigation development and of modification of hydrologic and hydrogeological characters after dams building. Quantitative estimation of recharge potentialities have been based on hydrological balance and groundwater table fluctuation calculations and on isotopic tracers techniques of the water molecule (δ18O, δ2H and 3H). This different methodological approaches used to estimate recharge rates have been useful, valuable and complementary. They give results fairly homogeneous and very interesting with indications accurate enough on recharge rates and on recharge spatio-temporal variations in shallow aquifers in alluvial plain (rate varying between 0-37% of annual rainfall) and dunes formations (rate varying between 0-44% of annual rainfall). Results indicate that recharge variations in term of proportions and of distribution are not only depending of volume and frequency rainfall or groundwater depth but also depending of soil and subsoil surface conditions, human activities (water withdraw, irrigation, market gardening, etc.) and evaporative demand. This recharge knowledge in terms of proportions and distribution in shallow aquifers is often very useful to propose groundwater resources management model and to define strategies to exploit them sustainably especially when groundwater resources are very unproductive and often very salty as in Senegal River delta.

Recharge Potentials Mapping using Remote Sensing and GIS Techniques: Case of Shallow Aquifers in the Senegal River Delta

Recharge Potentials Mapping using Remote Sensing and GIS Techniques: Case of Shallow Aquifers in the Senegal River Delta

Suitable management options to improve the productivity of rice cultivars under salinity stress

ABSTRACTGrowing rice in saline soils by minimizing damage on growth and yield remains a challenge. We conducted field experiments in the Africa Rice research field located in the Senegal River delta (16° 11ʹ N, 16° 15ʹ W) to study the effects of three management options of fertilization e.g. (i) nitrogen, phosphorus, and potassium fertilization: NPK; (ii) NPK combined with zinc: NPK-Zn, and (iii) NPK combined with gypsum: NPK-gypsum on the soil salinity level, the nutrient uptake and the productivity of different rice cultivars. The whole objective of this study is to determine how zinc or gypsum associated to NPK fertilizer can improve the growth and productivity of rice crop in saline soil. Results showed that the initial soil salinity level was reduced rapidly in plots treated with gypsum. The leaf-K/Na ratio, agronomic nitrogen use efficiency (ANUE), and grain yield of rice cultivars under the salinity stress were improved by the NPK-gypsum and NPK-Zn options relatively to the NPK option, suggesting that NPK-gypsum and NPK-Zn are suitable management options in reducing adverse effect of low K/Na, low ANUE as well as to improve rice yield under salinity stress.

Schistosomiasis in the Senegal River basin

Schistosomiasis in the Senegal River basin

Ecological distribution and population dynamics of Rift Valley fever virus mosquito vectors (Diptera, Culicidae) in Senegal

BackgroundMany zoonotic infectious diseases have emerged and re-emerged over the last two decades. There has been a significant increase in vector-borne diseases due to climate variations that lead to environmental changes favoring the development and adaptation of vectors. This study was carried out to improve knowledge of the ecology of mosquito vectors involved in the transmission of Rift Valley fever virus (RVFV) in Senegal.MethodsAn entomological survey was conducted in three Senegalese agro-systems, Senegal River Delta (SRD), Senegal River Valley (SRV) and Ferlo, during the rainy season (July to November) of 2014 and 2015. Mosquitoes were trapped using CDC light traps set at ten sites for two consecutive nights during each month of the rainy season, for a total of 200 night-traps. Ecological indices were calculated to characterize the different populations of RVFV mosquito vectors. Generalized linear models with mixed effects were used to assess the influence of climatic conditions on the abundance of RVFV mosquito vectors.ResultsA total of 355,408 mosquitoes belonging to 7 genera and 35 species were captured in 200 night-traps. RVFV vectors represented 89.02% of the total, broken down as follows: Ae. vexans arabiensis (31.29%), Cx. poicilipes (0.6%), Cx. tritaeniorhynchus (33.09%) and Ma. uniformis (24.04%). Comparison of meteorological indices (rainfall, temperature, relative humidity), abundances and species diversity indicated that there were no significant differences between SRD and SRV (P = 0.36) while Ferlo showed significant differences with both (P < 0.001). Mosquito collection increased significantly with temperature for Ae. vexans arabiensis (P < 0.001), Cx. tritaeniorhynchus (P = 0.04) and Ma. uniformis (P = 0.01), while Cx. poicilipes decreased (P = 0.003). Relative humidity was positively and significantly associated with the abundances of Ae. vexans arabiensis (P < 0.001), Cx. poicilipes (P = 0.01) and Cx. tritaeniorhynchus (P = 0.007). Rainfall had a positive and significant effect on the abundances of Ae. vexans arabiensis (P = 0.005). The type of biotope (temporary ponds, river or lake) around the trap points had a significant effect on the mosquito abundances (P < 0.001).ConclusionsIn terms of species diversity, the SRD and SRV ecosystems are similar to each other and different from that of Ferlo. Meteorological indices and the type of biotope (river, lake or temporary pond) have significant effects on the abundance of RVFV mosquito vectors.

Management strategies for coastal erosion problems in west Africa: Analysis, issues, and constraints drawn from the examples of Senegal and Benin

In West Africa, coastal erosion remains a problem for the socio-economic development of the coastal zone. Case studies in Senegal and Benin indicate a strong intensification of coastal erosion, in relation to human influence, as shown by the analysis of shoreline change rates from satellite data. The “Langue de Barbarie,” a sand spit bounding the mouth of the Senegal River delta in the Saint-Louis Region, Senegal, is relatively densely inhabited and developed. The spit was artificially breached in 2003 to alleviate potential river flooding that threatened the historical city of Saint-Louis. The analysis covers two periods: the pre-breach period (1984–2003) characterized by sectors alternating between erosion and accretion, and the post-breach period (2003–2016) indicating a generalization of the erosion process, with a noteworthy average rate of −3.72 m/yr affecting the entire spit, strongly destabilized by the artificial breach. In Benin, shoreline evolution is equally affected by human interventions. Following the construction of the Nangbéto Dam on the Mono River, the “Bouche du Roi,” outlet of this river, has been characterized by marked instability, with an eastward migration exceeding 700 m/yr. Other human alterations of the coastal system include the installment of major seaports and groins that have resulted in some erosion downdrift near Cotonou. These examples highlight the limits of governance regarding the coast in West Africa, including adaptation strategies developed at regional, national and local levels, which often produce more setbacks than solutions.